For that particular Team tab you need to go to the Project default layout page in Administration - Studio - Portlet pages
When you have the list of tabs displayed there is the translate icon next the name.
In some earlier versions you did not have your current language in the list so you would have to set the language to something else first before you could edit it. That does not seem to be the case in 15.2 where my language is English and English is in the list.